lib/crc32:
Hi,

This is an attempt to resolve all the issues that were left in the last review.
There is one proposed change that is still causing a difference of opinion
which has to do with the form of the loops and their performance on x86 and ppc
This version has the change to the form that runs faster on x86 as an ifdef.

This patch series provides improved performance for computing the crc32
polynomial on common hardware by adding the Slicing-by-8 algorithm to the
existing algorithms already included. The new algorithm is very closely
related to the existing algorithm so the extension requires small changes
to implement.  Additionally it cleans up some warnings in the existing
code and adds a kernel mode optional self test to replace the existing
user mode self test.

A description of the existing and new algorithm is included in
Documentation/crc32.txt.
Signed-off-by: Bob Pearson <rpearson@systemfabricworks.com>
Backported to .32 kernel by faux123
crc32: Bolt on crc32c
Reuse the existing crc32 code to stamp out a crc32c implementation.

Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
crc32: Select an algorithm via kconfig
Allow the kernel builder to choose a crc32* algorithm for the kernel.

Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
lib: Sparc's strncpy_from_user is generic enough, move under lib/
To use this, an architecture simply needs to:

1) Provide a user_addr_max() implementation via asm/uaccess.h

2) Add "select GENERIC_STRNCPY_FROM_USER" to their arch Kcnfig

3) Remove the existing strncpy_from_user() implementation and symbol
   exports their architecture had.

Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: David Howells <dhowells@redhat.com>
modified for Linux 3.0 Kernel from Linux 3.4+ by faux123
word-at-a-time: make the interfaces truly generic
This changes the interfaces in <asm/word-at-a-time.h> to be a bit more
complicated, but a lot more generic.

In particular, it allows us to really do the operations efficiently on
both little-endian and big-endian machines, pretty much regardless of
machine details.  For example, if you can rely on a fast population
count instruction on your architecture, this will allow you to make your
optimized <asm/word-at-a-time.h> file with that.

NOTE! The "generic" version in include/asm-generic/word-at-a-time.h is
not truly generic, it actually only works on big-endian.  Why? Because
on little-endian the generic algorithms are wasteful, since you can
inevitably do better. The x86 implementation is an example of that.

(The only truly non-generic part of the asm-generic implementation is
the "find_zero()" function, and you could make a little-endian version
of it.  And if the Kbuild infrastructure allowed us to pick a particular
header file, that would be lovely)

The <asm/word-at-a-time.h> functions are as follows:

 - WORD_AT_A_TIME_CONSTANTS: specific constants that the algorithm
   uses.

 - has_zero(): take a word, and determine if it has a zero byte in it.
   It gets the word, the pointer to the constant pool, and a pointer to
   an intermediate "data" field it can set.

   This is the "quick-and-dirty" zero tester: it's what is run inside
   the hot loops.

 - "prep_zero_mask()": take the word, the data that has_zero() produced,
   and the constant pool, and generate an *exact* mask of which byte had
   the first zero.  This is run directly *outside* the loop, and allows
   the "has_zero()" function to answer the "is there a zero byte"
   question without necessarily getting exactly *which* byte is the
   first one to contain a zero.

   If you do multiple byte lookups concurrently (eg "hash_name()", which
   looks for both NUL and '/' bytes), after you've done the prep_zero_mask()
   phase, the result of those can be or'ed together to get the "either
   or" case.

 - The result from "prep_zero_mask()" can then be fed into "find_zero()"
   (to find the byte offset of the first byte that was zero) or into
   "zero_bytemask()" (to find the bytemask of the bytes preceding the
   zero byte).

   The existence of zero_bytemask() is optional, and is not necessary
   for the normal string routines.  But dentry name hashing needs it, so
   if you enable DENTRY_WORD_AT_A_TIME you need to expose it.

This changes the generic strncpy_from_user() function and the dentry
hashing functions to use these modified word-at-a-time interfaces.  This
gets us back to the optimized state of the x86 strncpy that we lost in
the previous commit when moving over to the generic version.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
modified for Linux 3.0 from Linux 3.4+ by faux123
lib: add generic strnlen_user() function
This adds a new generic optimized strnlen_user() function that uses the
<asm/word-at-a-time.h> infrastructure to portably do efficient string
handling.

In many ways, strnlen is much simpler than strncpy, and in particular we
can always pre-align the words we load from memory.  That means that all
the worries about alignment etc are a non-issue, so this one can easily
be used on any architecture.  You obviously do have to do the
appropriate word-at-a-time.h macros.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
lib: Fix generic strnlen_user for 32-bit big-endian machines
The aligned_byte_mask() definition is wrong for 32-bit big-endian
machines: the "7-(n)" part of the definition assumes a long is 8
bytes.  This fixes it by using BITS_PER_LONG - 8 instead of 8*7.
Tested on 32-bit and 64-bit PowerPC.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
ARM: use generic strnlen_user and strncpy_from_user functions
This patch implements the word-at-a-time interface for ARM using the
same algorithm as x86. Although we have a clz instruction from ARMv5,
this only saves us one mov instruction when building with Thumb-2 and
makes no difference when targetting ARM, so we use the magic 0x0ff0001
constant for all CPUs. For big-endian configurations, we use the
implementation from asm-generic.

With this implemented, we can replace our byte-at-a-time strnlen_user
and strncpy_from_user functions with the optimised generic versions.

Signed-off-by: Will Deacon <will.deacon@arm.com>
modified for Linux 3.0 from Linux 3.4+ by faux123
kernel: Move REPEAT_BYTE definition into linux/kernel.h
And make sure that everything using it explicitly includes
that header file.

Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
modified for Linux 3.0 from Linux 3.4+ by faux123
update vm670_config
just for completeness